Heart rate variability in shift workers: responses to orthostatism and relationships with anthropometry, body composition, and blood pressure.

In order to investigate the response of heart rate variability (HRV) components to postural change and their association with cardiovascular risk factors in shift workers, a cross-sectional study with 438 Brazilian males rotating shift workers was done. Anthropometric, body composition, and clinical measures were collected. Electrocardiogram was recorded for 3 minutes, in the supine and orthostatic position, and HRV components were extracted. Descriptive analyses showed that mean values of body mass index, waist circumference (WC), waist-to-height ratio, visceral fat area (VFA), and blood pressure (BP) were higher than the reference values. In the regression model, age, WC, VFA, and systolic BP showed negative association with HRV components. These findings suggest the need for determining effective strategies for the evaluation and promotion of health among shift workers focused on the altered variables.

Lifetime shift work exposure: association with anthropometry, body composition, blood pressure, glucose and heart rate variability.

OBJECTIVE: To evaluate the association between lifetime exposure to shift work and blood pressure, fasting glucose (FG), anthropometric variables, body composition and heart rate variability (HRV). METHODS: Male shift workers (N=438) were evaluated using principal component (PC) analysis. The variables used were: weight, body mass index (BMI), waist circumference (WC), neck circumference (NC), hip circumference (HC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), body fat mass (BFKg), body fat percentage (BF%), visceral fat area (VFA), FG, systolic (SBP) and diastolic blood pressure (DBP), and HRV variables. ECG was performed, extracting heart rate (HR), root mean square of the successive differences (RMSSD), high frequency (HF), low frequency (LF) and the LF/HF ratio. Using linear regression models, the lifetime shift work exposure was associated with each PC. RESULTS: Five PCs were obtained, which accounted for 79.6% of the total variation of the data. PC1 (weight, BMI, WC, NC, HC, WHR, WHtR, BFKg, BF% and VFA) was designated as body obesity; PC2 (HF, RMSSD and LF) as good cardiac regulation; PC3 (SBP and DBP) as blood pressure; PC4 (LF/HF ratio and HR) as bad cardiac regulation and PC5 (WHR and FG) as insulin resistance. After age adjustment, the regression analysis showed that lifetime shift work was negatively associated with PC2 and positively associated with PC3. CONCLUSIONS: The association of lifetime shift work exposure with PC2 and PC3 suggests that shift work promotes unfavourable changes in autonomic cardiac control related to a decrease in parasympathetic modulation and an increase in blood pressure.

Reliability and validity of a semi-quantitative FFQ for sodium intake in low-income and low-literacy Brazilian hypertensive subjects.

OBJECTIVE: To assess the reliability and validity of an FFQ to evaluate dietary patterns of Na consumption among low-income and low-literacy Brazilian hypertensive subjects. DESIGN: The initial FFQ was submitted to content analysis with the pre-test administered to fifteen subjects. Reliability was evaluated according to the reproducibility criterion, with interviewer administration of the FFQ twice within a 15 d interval. Validity was assessed against a 24 h recall (132 subjects), a 3 d diet record (121 subjects) and a biomarker (24 h urinary Na; 121 subjects). To test the correlation with the biomarker, discretionary salt was added to the FFQ Na values. SETTING: A large urban teaching hospital in south-eastern Brazil. SUBJECTS: The study was based on 132 randomly selected subjects (eighty-three women and forty-nine men) aged 18 to 85 years. RESULTS: Kappa coefficients ranged from 0.79 to 0.98, confirming the reproducibility of the FFQ. There was no correlation between urinary Na excretion, the FFQ and the 24 h recall for the general sample, although significant correlations had been observed when methods were summed up (24 h recall + discretionary salt + FFQ; 0.32, P = 0.01). The addition of discretionary salt significantly improved the biomarker-based FFQ validity, with correlation coefficients varying from 0.19 (general sample) to 0.31 (female sub-sample). CONCLUSIONS: The developed FFQ demonstrated satisfactory evidence of validity and reliability and can be used as an important complementary tool for the evaluation of Na intake among Brazilian hypertensive subjects.